XVIth International Workshop on
Quantum Systems in
Chemistry and Physics
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Universal product angular-momentum distributions in photodissociation
and reaction collisions
O. S. Vasyutinskii
Ioffe Institute, Russian Academy of Sciences, 194021 St Petersburg, Russia
The field of stereodynamics and vector correlations in chemical and photochemical reactions
attracts much attention since decades. The importance of the vector properties in the reactions is based on the fact that practically all interactions within a reaction complex are intrinsically
anisotropic which in many cases results in the electronic and nuclear motion anisotropy in the reaction products. The talk reviews recent results on the full quantum mechanical treatment of the spin and orbital angular momentum recoil angle distributions of the products of chemical and photochemical reactions in diatomic and polyatomic molecules. The distributions obtained are presented in the body frame and in the molecular frame using the spherical tensor formalism. The main result is that the recoil angle distribution can be written, irrespective of the reaction mechanism, in a universal form in terms of the anisotropy-transforming coefficients KqKii c which contain all the information regarding the reaction dynamics, and can be either directly determined from experiment or calculated from theory.
The coefficients are scalar values which depend on the photofragment state multipole rank ( K), on the initial reagent spherical tensor rank ( Ki), and on component qi of the ranks K and Ki projected onto the recoil direction k. An important new conservation rule is revealed through the analysis, namely that the component qi is preserved in any scattering, or photolysis reaction. The coefficients KqKii c act as transformation coefficients between the angular momentum anisotropy of the reactants and that of the product. The results obtained are generalized to the case where the reaction reagents possess spin, or orbital electronic angular momentum polarization. General expressions for the anisotropy-transforming coefficients beyond the axial recoil limit contain scattering S-matrix elements and take into account all possible types of nonadiabatic interactions in the reaction complex, as well as the full range of possible coherence effects. Many important particular cases of these expressions are discussed. They are: (a) the role of Coriolis interactions in the photolysis of linear molecules which result is the molecular helicity non-conservation; (b) quasiclassical approximation of the molecular scattering function in the high- J limit. The talk also reviews recent experimental results on the photo-dissociation of a number of polyatomic molecules, and shows how the investigation of the values determined for the speed-dependent parameter â and higher-rank anisotropy parameters supported the interpretation of the photo-dissociation dynamics.
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References
[1] V. V. Kuznetsov and O. S. Vasyutinskii, J. Chem. Phys. 123, 034307 (2005).
[2] V. V. Kuznetsov and O. S. Vasyutinskii, J. Chem. Phys. 127, 044308 (2007).
[3] V. V. Kuznetsov, P. S. Shternin, O. S. Vasyutinskii, Phys. Scripta, 80, 048107 (2009)
[4] A. G. Smolin, O. S. Vasyutinskii, A..J. Orr-Ewing, Mol. Phys. 105, 885 (2007)
[5] P. S. Shternin and O.S. Vasyutinskii, J. Chem. Phys. 128, 194314 (2008).
[6] A. G. Suits and O. S. Vasyutinskii, Chem. Rev. 106, 3706 (2008).
[7] V. V. Kuznetsov, P. S. Shternin, O. S. Vasyutinskii, J. Chem. Phys., 130, 134312 (2009).
[8] G. G. Balint-Kurti and O. S. Vasyutinskii, J. Phys. Chem. A, 113, 14281 (2009).


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